In Scandinavian mythology, the eldest son of the dwarf king Hreidmar. The slaying of Fafnir represented the destruction of the demon of cold or darkness who had stolen the golden light of the sun. He slew for gold in Otter's skin; in form of dragon. He was a great worm who, in the Old German Tale of the Volsungs, guards the treasures of light, and is slain by Sigurd.